System Security : C code for Vigenere Cipher (should be executed in linux with gcc).

//Aim:To implement vigenere cipher in C. //Program: #include<stdio.h> void main() { int i; int kl; int pl; printf("Enter the length of the key stream. "); scanf("%d",&kl); printf("Enter the length of the plain text stream.(Without spaces) "); scanf("%d",&pl); char p[pl]; char k[kl]; printf("\nEnter the Key. "); for(i=-1;i<kl;++i) scanf("%c",&k[i]); printf("\nEnter the Plain text. "); for(i=-1;i<pl;++i) scanf("%c",&p[i]); int s[3][pl]; for(i=0;i<pl;++i) { if(65<=p[i] && p[i]<=91) s[0][i]=p[i]%65; else s[0][i]=p[i]%97; } for(i=0;i<pl;++i) printf("%d ",s[0][i]); int count=0; while(count<pl) { for(i=0;i<kl;++i) { if(65<=k[i] && k[i]<=91) s[1][count+i]=k[i]%65; else s[1][count+i]=k[i]%97; } count=count+kl; } printf("\n"); for(i=0;i<pl;++i) printf("%d ",s[1][i]); printf("\n"); for(i=0;i<pl;++i) printf("%d ",s[2][i]); printf("\n\nThe cipher text is: "); char cipher[kl]; for(i=0;i<pl;++i) { s[2][i]=(s[0][i]+s[1][i])%26; cipher[i]=(char)(s[2][i]+65); printf("%c ",cipher[i]); } } /*Output lab2@lab2-OptiPlex-330:~/Desktop$ gcc vigenere.c lab2@lab2-OptiPlex-330:~/Desktop$ ./a.out Enter the length of the key stream. 6 Enter the length of the plain text stream.(Without spaces) 14 Enter the Key. pascal Enter the Plain text. sheislistening 18 7 4 8 18 11 8 18 19 4 13 8 13 6 15 0 18 2 0 11 15 0 18 2 0 11 15 0 The cipher text is: H H W K S W X S L G N T C G */

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System Security : C code for Hill Cipher (should be executed in linux with gcc).

//Aim:To implement Hill Cipher in C //Program: #include<stdio.h> int check(int x) { if(x%3==0) return 0; int a=x/3; int b=3*(a+1); int c=b-x; return c; } void main() { int l,i,j; int temp1; int k[3][3]; int p[3][1]; int c[3][1]; char ch; printf("\nThe cipher has a key of length 9. ie. a 3*3 matrix.\nEnter the 9 character key. "); for(i=0;i<3;++i) { for(j=0;j<3;++j) { scanf("%c",&ch); if(65<=ch && ch<=91) k[i][j]=(int)ch%65; else k[i][j]=(int)ch%97; } } for(i=0;i<3;++i) { for(j=0;j<3;++j) { printf("%d ",k[i][j]); } printf("\n"); } printf("\nEnter the length of string to be encoded(without spaces). "); scanf("%d",&l); temp1=check(l); if(temp1>0) printf("You have to enter %d bogus characters.",temp1); char pi[l+temp1]; printf("\nEnter the string. "); for(i=-1;i<l+temp1;++i) { scanf("%c",&pi[i]); } int temp2=l; int n=(l+temp1)/3; int temp3; int flag=0; int count; printf("\n\nThe encoded cipher is : "); while(n>0) { count=0; for(i=flag;i<flag+3;++i) { if(65<=pi[i] && pi[i]<=91) temp3=(int)pi[i]%65; else temp3=(int)pi[i]%97; p[count][0]=temp3; count=count+1; } int k1; for(i=0;i<3;++i) c[i][0]=0; for(i=0;i<3;++i) { for(j=0;j<1;++j) { for(k1=0;k1<3;++k1) c[i][j]+=k[i][k1]*p[k1][j]; } } for(i=0;i<3;++i) { c[i][0]=c[i][0]%26; printf("%c ",(char)(c[i][0]+65)); } n=n-1; flag=flag+3; } } /*OUTPUT [adi@localhost Desktop]$ gcc hill.c [adi@localhost Desktop]$ ./a.out The cipher has a key of length 9. ie. a 3*3 matrix. Enter the 9 character key. GYBNQKURP 6 24 1 13 16 10 20 17 15 Enter the length of string to be encoded(without spaces). 6 Enter the string. actCAt The encoded cipher is : P O H F I N [adi@localhost Desktop]$ gcc hill.c [adi@localhost Desktop]$ ./a.out The cipher has a key of length 9. ie. a 3*3 matrix. Enter the 9 character key. GYBNQKURP 6 24 1 13 16 10 20 17 15 Enter the length of string to be encoded(without spaces). 7 You have to enter 2 bogus characters. Enter the string. actcatact The encoded cipher is : P O H F I N P O H */

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Robotics & AI: Java code for Homogeneous Composite Transformation Matrix (HCTM) finding fixed , mobile co-ordinates.

//Aim: To implement fixed and mobile co-ordinates in JAVA //Program import java.util.*; class htmc { static int m1[][]={ {3,0,0},{0,2,1},{0,-1,2}}; static int m2[][]={ {2,0,-1},{0,3,0},{1,0,2}}; static int m3[][]={ {2,1,0},{-1,2,0},{0,0,3}}; static double pm[][]=new double[3][1]; static double pf[][]=new double[3][1]; static double p[][]=new double[3][3]; static int a,t; static void mat_mul() { for(int i=0;i<3;++i) pf[i][0]=0; for(int i=0;i<3;++i) { for(int j=0;j<1;++j) { for(int k=0;k<3;++k) pf[i][j]+=p[i][k]*pm[k][j]; } } } static void get_m1() { double temp; for(int i=0;i<3;++i) { for(int j=0;j<3;++j) { if(m1[i][j]==2) p[i][j]=Math.cos(Math.toRadians(t)); else if(m1[i][j]==3) p[i][j]=1; else { temp=90+m1[i][j]*t; p[i][j]=Math.cos(Math.toRadians(temp)); } } } } static void get_m2() { double temp; for(int i=0;i<3;++i) { for(int j=0;j<3;++j) { if(m2[i][j]==2) p[i][j]=Math.cos(Math.toRadians(t)); else if(m2[i][j]==3) p[i][j]=1; else { temp=90+m2[i][j]*t; p[i][j]=Math.cos(Math.toRadians(temp)); } } } } static void get_m3() { double temp; for(int i=0;i<3;++i) { for(int j=0;j<3;++j) { if(m3[i][j]==2) p[i][j]=Math.cos(Math.toRadians(t)); else if(m3[i][j]==3) p[i][j]=1; else { temp=90+m3[i][j]*t; p[i][j]=Math.cos(Math.toRadians(temp)); } } } } public static void main(String args[]) { Scanner scr=new Scanner(System.in); System.out.println("Enter [P]m values. "); for(int i=0;i<3;++i) { pm[i][0]=scr.nextDouble(); } System.out.println("Rotation about which axis? 1,2,3 "); a=scr.nextInt(); System.out.println("Enter the angle "); t=scr.nextInt(); if(a==1) get_m1(); else if(a==2) get_m2(); else get_m3(); mat_mul(); System.out.println("The [P]f matrix is as follows. "); for(int i=0;i<3;++i) System.out.println(pf[i][0]); int temp1; for(int i=0;i<3;++i) { for(int j=0;j<3;++j) { p[i][j]=(p[i][j]*100); temp1=(int)p[i][j]; p[i][j]=temp1/100.0; } } System.out.println("\nThe final HTMC matrix is as follows."); for(int i=0;i<3;++i) { for(int j=0;j<3;++j) { System.out.print(p[i][j]+"\t"); } System.out.print(pm[i][0]+"\n"); } System.out.print("\n0\t0\t0\t1"); } } /*OUTPUT C:\Users\Aditya\Desktop\aditya>javac htmc.java C:\Users\Aditya\Desktop\aditya>java htmc Enter [P]m values. 2 0 3 Rotation about which axis? 1,2,3 1 Enter the angle 60 The [P]f matrix is as follows. 2.0 -2.598076211353316 1.5000000000000007 The final HTMC matrix is as follows. 1.0 0.0 0.0 2.0 0.0 0.5 -0.86 0.0 0.0 0.86 0.5 3.0 0 0 0 1 */

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System Security : C code for Additive cipher / Shift cipher / Caeser cipher ( can be executed in Linux )

In cryptography, a Caesar cipher, also known as Caesar's cipher, the shift cipher, Caesar's code or Caesar shift, is one of the simplest and most widely known encryption techniques. It is a type of substitution cipher in which each letter in the plain text is replaced by a letter some fixed number of positions down the alphabet. For example, with a left shift of 3, D would be replaced by A, E would become B, and so on. The method is named after Julius Caeser, who used it in his private correspondence.
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Given below is the C code for the same.

//Aim: To implement additive cipher in C //Program: #include<stdio.h> void main() { char c[20]; int a1[20]; int a2[20]; int n=0; int k=0; printf("\nPlease Enter the key value: "); scanf("%d",&k); printf("\nHow many letters in the text? : "); scanf("%d",&n); int i; printf("\nPlease enter a word to be encoded:"); for(i=-1;i<n;++i) { scanf("%c",&c[i]); } int temp=0; int j=0; int count=0; for(i=0;i<=n;++i) { l1:temp=(int)c[i]; if(c[i]==' ') { i=i+1; count=count+1; goto l1; } if(65<=temp && temp<=91) a1[j]=temp%65; else if(97<=temp<=123) a1[j]=temp%97; a2[j]=(a1[j]+k)%26; ++j; } n=n-count; printf("\nThe encoded cipher is: "); char c2[20]; for(i=0;i<n;++i) { c2[i]=(char)(a2[i]+97); printf("%c",c2[i]); } printf("\n\nDecoding it receiver side "); int a3[20]; for(i=0;i<n;++i) a3[i]=(int)(c2[i]-97); for(i=0;i<n;++i) { if(a3[i]>=k) a3[i]=a3[i]-k; else a3[i]=a3[i]-15+26; } printf("\nThe text is: "); for(i=0;i<n;++i) { printf("%c",(char)(a3[i]+97)); } } /*OUTPUT Please Enter the key value: 15 How many letters in the text? : 5 Please enter a word to be encoded:hello The encoded cipher is: wtaad Decoding it receiver side The text is: hello Please Enter the key value: 15 How many letters in the text? : 12 Please enter a word to be encoded:good morning The encoded cipher is: vddsbdgcxcv Decoding it receiver side The text is: goodmorning */

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